Double-clutch transmission for vehicles

ABSTRACT

A double-clutch transmission includes, but is not limited to an inner input shaft inside an outer input shaft. Two clutch discs are connected to the two input shafts, respectively. Three layshafts of the DCT are parallel to the input shafts and one of the layshafts has a pinion at en end. Gearwheels on the shafts include, but are not limited to seven gearwheel groups for providing seven sequentially increasing forward gears. Each of the groups comprises a fixed gearwheel on the inner input shaft, meshing with an idler gearwheel on one of the layshafts for providing a forward gear. A fourth fixed gearwheel meshes with a fourth gear idler gearwheel and a sixth gear idler gearwheel. Especially, the DCT further includes, but is not limited to comprises the double-clutch transmission that includes, but is not limited to a park-lock gearwheel fixed onto one of the layshafts that carries a final drive pinion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National-Stage entry under 35 U.S.C. §371based on International Application No. PCT/EP2009/002353, filed Mar. 31,2009, which was published under PCT Article 21(2) and which claimspriority to European Application No. 08006645.9, filed Mar. 31, 2008,and which claims priority to European Application No. 08006638.4, filedMar. 31, 2008, and which claims priority to European Application No.08006639.2, filed Mar. 31, 2008, and which claims priority to EuropeanApplication No. 08006640.0, filed Mar. 31, 2008, and which claimspriority to European Application No. 08006641.8, filed Mar. 31, 2008,and which claims priority to European Application No. 08006642.6, filedMar. 31, 2008, and which claims priority to European Application No.08006635.0, filed Mar. 31, 2008, and which claims priority to EuropeanApplication No. 08006643.4, filed Mar. 31, 2008, and which claimspriority to European Application No. 08006644.2, filed Mar. 31, 2008,and which claims priority to European Application No. 08006486.8, filedMar. 31, 2008, and which claims priority to European Application No.08006606.1, filed Mar. 31, 2008, and which claims priority to EuropeanApplication No. 08006607.9, filed Mar. 31, 2008, and which claimspriority to European Application No. 08006608.7, filed Mar. 31, 2008,and which claims priority to European Application No. 08006646.7, filedMar. 31, 2008, and which claims priority to European Application No.08006616.7, filed Mar. 31, 2008, and which claims priority to EuropeanApplication No. 08006617.8, filed Mar. 31, 2008, and which claimspriority to European Application No. 08006609.5, filed Mar. 31, 2008,and which claims priority to European Application No. 08006610.3, filedMar. 31, 2008, and which claims priority to European Application No.08006611.1, filed Mar. 31, 2008, and which claims priority to EuropeanApplication No. 08006612.9, filed Mar. 31, 2008, and which claimspriority to European Application No. 08006621.0, filed Mar. 31, 2008,and which claims priority to European Application No. 08006622.8, filedMar. 31, 2008, and which claims priority to European Application No.08006623.6, filed Mar. 31, 2008, and which claims priority to EuropeanApplication No. 08006624.4, filed Mar. 31, 2008, and which claimspriority to European Application No. 08006569.1, filed Mar. 31, 2008,and which claims priority to European Application No. 08006637.6, filedMar. 31, 2008, and which claims priority to European Application No.08006615.2, filed Mar. 31, 2008, and which claims priority to EuropeanApplication No. 08006636.8, filed Mar. 31, 2008, and which claimspriority to European Application No. 08006625.1, filed Mar. 31, 2008,and which claims priority to European Application No. 08006626.9, filedMar. 31, 2008, and which claims priority to European Application No.08006627.7, filed Mar. 31, 2008, and which claims priority to EuropeanApplication No. 08006628.5, filed Mar. 31, 2008, and which claimspriority to European Application No. 08006629.3, filed Mar. 31, 2008,and which claims priority to European Application No. 08006630.1, filedMar. 31, 2008, and which claims priority to European Application No.08006631.9, filed Mar. 31, 2008, and which claims priority to EuropeanApplication No. 08006619.4, filed Mar. 31, 2008, and which claimspriority to European Application No. 08006620.2, filed Mar. 31, 2008,and which claims priority to European Application No. 08006618.6, filedMar. 31, 2008, and which claims priority to European Application No.08006614.5, filed Mar. 31, 2008, and which claims priority to EuropeanApplication No. 08006613.7, filed Mar. 31, 2008, and which claimspriority to European Application No. 08006634.3, filed Mar. 31, 2008,and which claims priority to European Application No. 08006633.5, filedMar. 31, 2008, and which claims priority to European Application No.08006632.7, filed Mar. 31, 2008, and which claims priority to EuropeanApplication No. 08006649.1, filed Mar. 31, 2008, and which claimspriority to European Application No. 08006648.3, filed Mar. 31, 2008,and which claims priority to European Application No. 08006647.5, filedMar. 31, 2008, which are all hereby incorporated in their entirety byreference.

TECHNICAL FIELD

The present application relates to a double-clutch transmission forvehicles, such as cars.

BACKGROUND

A double-clutch transmission (DCT) comprises two input shafts that areconnected to and actuated by two clutches separately. The two clutchesare often combined into a single device that permits actuating any ofthe two clutches at one time. The two clutches transmit driving torquefrom an engine to the two input shafts of the double-clutchtransmission.

Volkswagen has provided a 7-speed dual clutch gearbox (DSG®), namelyDQ200. The DSG® DQ200 provides an attempt to provide a 7-speed dualclutch gearbox in the cars for street driving.

The DCT has not yet been widely used in cars for street driving.Problems that hinder the application of DCT for street driving comprisea provision of a compact, reliable, and fuel-efficient DCT. Therefore,there exists a need for providing such a DCT that is also affordable byconsumers.

SUMMARY

The present application provides a double-clutch transmission (DCT) thatcomprises an inner input shaft and an outer input shaft. The outer inputshaft surrounds a portion of the inner input shaft. The outer inputshaft surrounds the inner input shaft in a radial direction. The radialdirection indicates regions that surround a longitudinal axis of theinner input shaft. The outer input shaft can be a hollow input shaft andthe inner input shaft can be a solid input shaft. Alternatively, theinner input shaft can also be a hollow input shaft.

The DCT comprises a first clutch disc that is connected non-rotatably tothe inner input shaft and a second clutch disc that is also connectednon-rotatably to the outer input shaft. For example, the first clutchdisc is fixed to the inner input shaft and the second clutch disc isfixed to the outer input shaft. Alternatively, a universal joint canprovide the non-rotatable connection.

The DCT has a first layshaft, a second layshaft, and a third layshaftthat are spaced apart from the input shafts and arranged in parallel tothe input shafts. That is, longitudinal axes of these shafts areparallel to each other, including overlapping axes. One of more of thelayshafts comprises a pinion as a final drive. The pinion can mesh withan output gear wheel on an output shaft for outputting a drive torque toa drive train of a vehicle. The drive train can alternatively bereferred as powertrain or powerplant that comprises the group ofcomponents for generating power and for delivering it to the roadsurface, water, or air. The drive train can include an engine, atransmission, drive shafts, differentials, and a final drive. The finaldrive can include drive wheels, continuous track that is used in tanksor caterpillar tractors, or propeller.

Gearwheels of the DCT are arranged on the first layshaft, on the secondlayshaft, on the third layshaft, on the inner input shaft and on theouter input shaft. These gearwheels comprise a first gearwheel group, asecond gearwheel group, a third gearwheel group, a fourth gearwheelgroup, a fifth gearwheel group, a sixth gearwheel group, and a seventhgearwheel group for providing seven sequentially increasing forwardgears. The gear of the DCT can refer to an output speed range of theoutput gear wheel. The sequentially increasing gears describe anescalating order that members of the order follow each other. Gears of acar can be arranged in a sequentially increasing manner from a firstgear to a seventh gear. Gear ratios of the DCT decrease from the firstgear to the seventh gear correspondingly. For example, in a car having aDCT of seven gears, a first gear has a gear ratio of 2.97:1. A secondgear has a gear ratio of 2.07:1. A third gear has a gear ratio of1.43:1. A fourth gear has a gear ratio of 1.00:1. A fifth gear has agear ratio of 0.84:1. A sixth gear has a gear ratio of 0.56:1. Lastly, aseventh gear has a gear ratio of 0.32:1. The seven gears provide anincreasing order of output speed ranges of the transmission for drivinga car with the DCT.

The first gearwheel group comprises a first fixed gearwheel on the innerinput shaft, meshing with a first gear idler gearwheel on one of thelayshafts for providing a first forward gear. The third gearwheel groupcomprises a third fixed gearwheel on the inner input shaft, meshing witha third idler gearwheel on one of the layshafts for providing a thirdforward gear. The fifth gearwheel group comprises a fifth fixedgearwheel on the inner input shaft, meshing with a fifth gear idlergearwheel on one of the layshafts for providing a fifth forward gear.The seventh gearwheel group comprises a seventh fixed gearwheel on theinner input shaft, meshing with a seventh gear idler gearwheel on one ofthe layshafts for providing a seventh forward gear.

The second gearwheel group comprises a second fixed gearwheel on theouter input shafts, meshing with a second gear idler gearwheel on one ofthe layshafts for providing a second forward gear. The fourth gearwheelgroup comprises a fourth fixed gearwheel on the outer input shafts,meshing with a fourth gear idler gearwheel on one of the layshafts forproviding a fourth forward gear. The sixth gearwheel group comprises asixth fixed gearwheel on the outer input shafts, meshing with a sixthgear idler gearwheel on one of the layshafts for providing a sixthforward gear.

One or more gearwheel groups comprise a coupling device which isarranged on one of the layshafts to selectively engage one of thegearwheels for selecting one of the seven gears. The fourth fixedgearwheel further meshes with the six gear idler gearwheel.

Especially, the double-clutch transmission further comprises a park-lockgearwheel fixed onto one of the layshafts that carries the pinion as afinal drive pinion. The layshaft with the park-lock comprises the finaldrive pinion for engaging and for locking a differential of the DCT. Thedifferential comprises the output gearwheel on the output shaft. Thepark-lock enables a vehicle with the park-lock to park at a place in asecure manner, even on a slope. The park-lock is easy to implement andbeneficial for the vehicle and passengers' safety.

The DCT provides seven forward gears through a dual clutch. The DCTmakes gear switching between odd and even ratios to be swift andefficient because the gearwheels of the odd and even gears are driven bydifferent clutch discs or by different clutches respectively. One doublemeshing feature is provided by the fourth fixed gearwheel that mesheswith the fourth gear idler gearwheel and the sixth gear idler gearwheel.The double meshing feature makes the DCT to be compact and lightweightat low cost because two fixed gearwheels are avoided on the inputshafts. An idler gearwheel and a coupling device together can replace afixed gearwheel on one of the input shafts. Similarly, an idlergearwheel on one of the layshafts can be replaced by a fixed gearwheelif an idler together with a coupling device are provided on one of theinput shafts for meshing with the fixed gearwheel on one of thelayshafts.

In the application, one of the fixed gearwheels of a lower gear on oneof the input shafts can be mounted closer to clutch disc ends of theinput shafts than another one of the fixed gearwheel of a higher gear.The clutch disc ends of the input shafts are the ends of the inputshafts for coupling with the two clutch discs. Idler gearwheels of thelower gears on one of the layshafts are larger than that of highergears. Since a clutch-housing has a large compartment around the pinionsand the clutch disc ends, the compartment can be utilized to enclose thelarger idler gearwheels of lower gears. As result, the clutch housingthat encloses ends of layshafts without the pinions can be made withsmaller, which enables the double-clutch transmission to be morecompact. Therefore, it is beneficial to have an idler gearwheel of alower gear closer to a pinion on a same layshaft.

Since the idler and fixed gearwheels of the same gear mesh with eachother, it is beneficial to mount a fixed gearwheel of a lower gear onthe input shaft to be closer to the clutch disc ends of the inputshafts.

In one embodiment, the application can provide the seventh gear idlergearwheel on the second layshaft to be the most remote from the pinion,as compared to other idlers on the same layshaft. In another embodiment,the application can provide the seventh fixed gearwheel to be moreremote to the clutch disc ends of the input shafts than the first fixedgearwheel.

One of the idler gearwheels of a lower gear is closer to the pinion thananother one of the idler gearwheels of a higher gear on their sharedlayshaft.

In the application, the two different input shafts can drive or providethe first forward gear and the reverse gear separately. Dual clutches ofthe DCT enables that the switching between the two input shafts can beachieved quickly. As a result, a driving scheme that the DCT engages thetwo input shafts alternatively can drive the vehicle back & forthrapidly. This scheme is useful for moving the vehicle out of a muddypuddle because the vehicle can simply be driven back & forth to get outthe puddle. Less loss of momentum of the gearwheels and the layshafts ofthe DCT can be achieved. Alternatively, the back and forth movements canbe provided by a second forward gear and a first reverse gear ondifferent input shafts.

The gearwheels can further comprise a reverse gearwheel group thatcomprises a reverse fixed gearwheel on one of the input shafts, meshingwith a first reverse gear wheel on the third layshaft for receiving aninput reverse torque. The reverse gearwheel group can further comprise asecond reverse gear wheel on the third layshaft that meshes with one ofthe idler gearwheels on one of the first layshaft and the secondlayshaft for outputting the received reverse torque to the pinion. Thereverse gearwheel group can further comprise a coupling device on one ofthe layshafts to engage the gearwheels of the reverse gear for selectingthe reverse gear. The reverse gear makes the vehicle with the DCT to bemore maneuverable.

The double-clutch transmission device can comprise two pinions that aremounted on two of the layshafts respectively. The two pinions can meshor comb with one relatively big output gearwheel on an output shaft. Theoutput gearwheel can be integrated into a transmission differentialdevice without providing an intermediate output shaft of thetransmission gearbox. This allows a very dense packaging situation forthe DCT.

According to the application, two or more of the first gear idlergearwheel, the second gear idler gearwheel, and the third gear idlergearwheel are mounted on the same layshaft. Putting idler gearwheels oflow gears, such as idler gearwheels of the first, second and thirdgears, on the same shaft require the layshaft to be strong and sturdy.Remaining layshafts of the double-clutch transmission can thus be madeslim at low cost for carrying gearwheels of high gears, except thelayshaft carrying reverse gear idler gearwheel. For example, two or morethe fourth gear idler gearwheel, the fifth gear idler gearwheel, thesixth gear idler gearwheel and the seventh gear idler gearwheel aremounted on the same layshaft.

The double-clutch transmission can further comprise bearings forsupporting the layshafts. One or more of the bearings is provided nextto the pinion. The immediate adjacent bearing reduces deflection of thelayshaft under load to better support the pinion that outputs torque ofits carrying layshaft. The supporting bearing thus can improve torquetransmission efficiency and reduce cost of the DCT.

One or more the bearings are provided next to one of the drivengearwheels of low gears. Gearwheels of low gears transmit larger torquesas compared to the gearwheels of high gears. Close support of thebearings help to reduce excessive deflection and weight related cost oftheir carrying shafts.

The application provides a gearbox that comprises the double-clutchtransmission and an output gearwheel on an output shaft. The outputgearwheel meshes with the pinion for outputting a drive torque to atorque drain. The output gearwheel can even mesh with each of thepinions. The output gearwheel provides a single source of torque outputso that the construction of the DCT is made simple and neat.

The application provides a power train device with the gearbox. One ormore of power source generates a driving torque. The power train deviceusually has the gearbox and the power source onboard so that a vehiclewith the power train device can be mobile without being physicallyattached to an external stationary power source.

The power source can comprise a combustion engine. The power train withthe combustion engine and the DCT is easy to manufacture. The combustionengine can consume less petrol for environmental protection.Furthermore, a combustion engine usable for other types of fuel can haveeven less polluting emission, such as hydrogen fuel.

The power source can comprise an electric motor. Electric motor used ina hybrid car, or in an electrical car enables reduction of pollution, ascompared to typical combustion using petrol. The electric motor can evenrecuperate brake energy in a generator mode.

The application also provides a vehicle that comprises the power traindevice. The vehicle having the power train device is efficient in energyusage by using the DCT.

The double clutch transmission enables pre-selection of gears for smoothgear transmission. Two coupling devices can engage the idler gearwheelof the current gear and the idler gearwheel of the next sequential gearat the same time. This allows the next sequential gear to be connectedrapidly and thus in a more smooth manner. In particular, the two idlersof two consecutive gears that are driven by different input shafts ofthe DCT can be both engaged simultaneously. For example, idlergearwheels of the fourth gear and the fifth gear of the DCT can be bothengaged to their weight-carrying layshaft by their respectively couplingdevices when one of the input shafts receives an input torque. Oneengaged idler gearwheel is driven directly by the input torque whilstthe other engaged idler gearwheel is driven via the pinion by the inputtorque. In this manner, little or no interruption in torque flow duringgearshift. Therefore, the double-clutch transmission provides continuousand more efficient torque transmission, as compared to other gearshiftprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and

FIG. 1 illustrates a front view of a first embodiment of a double clutchtransmission of the application;

FIG. 2 illustrates the path of torque flow of a first gear transmissionratio;

FIG. 3 illustrates the path of torque flow of a second gear transmissionratio;

FIG. 4 illustrates the path of torque flow of a third gear transmissionratio;

FIG. 5 illustrates the path of torque flow of a fourth gear transmissionratio;

FIG. 6 illustrates the path of torque flow of a fifth gear transmissionratio;

FIG. 7 illustrates the path of torque flow of a sixth gear transmissionratio;

FIG. 8 illustrates the path of torque flow of a seventh geartransmission ratio;

FIG. 9 illustrates the path of torque flow of a reverse geartransmission ratio;

FIG. 10 illustrates an assembly of a double-sided coupling device withits neighboring gearwheels for engagement;

FIG. 11 illustrates an assembly of a single-sided coupling device withits neighboring gearwheel for engagement;

FIG. 12 illustrates an assembly of an idler gearwheel that is rotatablysupported by a shaft on a bearing;

FIG. 13 illustrates an assembly of a fixed gearwheel that is supportedon a shaft;

FIG. 14 illustrates a cross-section through a detail of a crankshaft ofan internal combustion engine according to embodiment of thedouble-clutch transmission;

FIG. 15 illustrates a front view of a further embodiment of a doubleclutch transmission of the application;

FIG. 16 illustrates an expanded side view of the double clutchtransmission of FIG. 15;

FIG. 17 illustrates a front view of a further embodiment of a doubleclutch transmission of the application; and

FIG. 18 illustrates an expanded side view of the double clutchtransmission of FIG. 17.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit application and uses. Furthermore, there is nointention to be bound by any theory presented in the precedingbackground or summary or the following detailed description.

In the following description, details are provided to describe theembodiments of the application. It shall be apparent to one skilled inthe art, however, that the embodiments may be practiced without suchdetails.

FIGS. 1-14 provide detailed description of an embodiment of a doubleclutch transmission (DCT) of the application. FIGS. 1-14 comprisesimilar parts that have similar reference numbers. Relevant descriptionof the similar parts is incorporated where necessary.

FIG. 1 illustrates a front view of an embodiment of a double clutchtransmission 1 of the application. The DCT 1 comprises a reverse gearidler shaft 38, an upper pinion 41 on an upper layshaft 40, two inputshafts 20, 22, a lower pinion 51 on a lower layshaft 50, and arelatively large output gearwheel 12 on an output shaft 14. The twoinput shafts 20, 22 comprise an inner input shaft 20 and an outer inputshaft 22. The inner input shaft 20 is a solid input shaft 20 (i.e. K1)and the outer input shaft is a hollow input shaft 22 (i.e. K2). Thesolid input shaft 20 and the hollow input shaft 22 share the samelongitudinal axis of rotation. The two pinions 41, 51 are fixed to rightends of the upper layshaft 40 and the lower layshaft 50 respectively.The output gearwheel 12 is also fixed to the output shaft 14 along itslongitudinal axis. The two pinions 41, 51 mesh with the output gearwheel12 separately at different positions of the output gearwheel 12.

The reverse gear idler shaft 38, the upper layshaft 40, and the lowerlayshaft 50 are parallel to the coaxial input shafts 20, 22 withpredetermined distances in-between. The distances are provided in radialdirections of these shafts respectively, which is better seen in FIG. 2.Other gearwheels are mounted on these shafts that mesh with each otheraccording to predetermined manners. These manners are better seen insome of the following figures.

FIG. 1 further shows a cutting plane A-A for illustrating an expandedcross-section view through the DCT 1, which is shown in FIGS. 2 to 9.The cutting plane A-A passes through the rotational axes of the reversegear shaft 38, the upper layshaft 40, the input shafts 20, 22, the lowerlayshaft 50, and the output shaft 14. One of the goals of FIGS. 2 to 9is to illustrate further structure and torque flows of the DCT 1.

FIG. 2 illustrates the expanded view of the DCT that shows the mannersof the gearwheels mounting, which corresponds to FIG. 1.

According to FIG. 2, the DCT 1 comprises the following shafts, from topto bottom, the reverse gear shaft 38, the upper layshaft 40, the hollowinput shaft 22, the solid input shaft 20, the lower layshaft 50, and theoutput shaft 14. The solid input shaft 20 is partially disposed insidethe hollow input shaft 22. The solid input shaft 20 also protrudesoutside the hollow input shaft 22 at two ends. The hollow input shaft 22is mounted onto the solid input shaft 20 by a pair of solid shaftbearings 71 that are disposed between the solid input shaft 20 and thehollow input shaft 22 at two ends of the hollow input shaft 22. As aresult, the two input shafts 20, 22 are coupled together such that thesolid input shaft 20 is free to rotate inside the hollow input shaft 22.The hollow input shaft 22 surrounds a right portion of the solid inputshaft 20, and a left portion of the solid input shaft 20 is exposedoutside the hollow input shaft 22. The assembly of the input shafts 20,22 is supported by the solid shaft bearing 71 at a protruding end of thesolid shaft 20 on the left and by the hollow shaft bearing 72 on thehollow input shaft 22 on the right.

According to FIG. 2, the outer input shaft 22 in a radial direction ofthe solid input shafts 20 surrounds a portion of the solid input shaft20. The radial direction is perpendicular to the common longitudinalaxes of the input shafts 20, 22. There are four gearwheels fixed on theleft exposed portion of the solid input shaft 20. These gearwheels are afixed wheel first gear 24, a fixed wheel seventh gear 27, a fixed wheelthird gear 25 and a fixed wheel fifth gear 26 from right to leftsequentially. Each of the fixed wheel first gear 24, the fixed wheelseventh gear 27, the fixed wheel third gear 25 and the fixed wheel fifthgear 26 is mounted onto the solid input shaft 20 coaxially. On thehollow input shaft 22, which is mounted on the right portion of thesolid input shaft 20, there are attached with a fixed wheel fourth gear31 and a fixed wheel second gear 30 from left to right. The fixed wheelfourth gear 31 also serves as a fixed wheel sixth gear 32. Each of thefixed wheel fourth gear 31 and the fixed wheel second gear 30 is fixedonto the hollow input shaft 22 coaxially.

The upper layshaft 40 is provided above the input shafts 20, 22. Thereare gearwheels, coupling devices and bearings provided on the upperlayshaft 40. These includes, from right to the left, the upper pinion41, a layshaft bearing 73, a reverse gear idler wheel 37, a double-sidedcoupling device 81, an idler sixth gear 65, an idler fifth gear 64, adouble-sided coupling device 82, an idler seventh gear 66, and alayshaft bearing 73.

The reverse gear idler wheel 37, the idler sixth gear 65, the idlerfifth gear 64, and the idler seventh gear 66 are mounted on the upperlayshaft 40 by bearings respectively such that these gearwheels are freeto rotate around the upper layshaft 40. The double-sided coupling device81 can move along the upper layshaft 40 to engage any of the 37 and the65 to the upper layshaft 40. Similarly, the double-sided coupling device82 can move along the upper layshaft 40 to engage any of the idler fifthgear 64 and the idler seventh gear 66 to the upper layshaft 40. Theidler sixth gear 65 meshes with the fixed wheel sixth gear 32. The idlerfifth gear 64 meshes with the fixed wheel fifth gear 26. The idlerseventh gear 66 meshes with the fixed wheel seventh gear 27.

The reverse gear idler shaft 38 is provided further above the upperlayshaft 40. An idle shaft bearing 74, a first reverse gear wheel 35, asecond reverse gear wheel 36 and an idle shaft bearing 74 are mountedonto the reverse gear shaft 38 from right to left. Both the firstreverse gear wheel 35 and the second reverse gear wheel 36 are fixedonto the reverse gear idler shaft 38 coaxially such that the firstreverse gear wheel 35 and the second reverse gear wheel 36 rotatestogether with the reverse gear idler shaft 38. The first reverse gearwheel 35 meshes with the fixed wheel second gear 30. The second reversegear wheel 36 meshes with the reverse gear idler wheel 37.

The lower layshaft 50 is provided below the input shafts 20, 22. Aplurality of components is mounted on the lower layshaft 50. Thecomponents include gearwheels, coupling devices and bearings. Thecomponents comprises, from right to the left, the lower pinion 51, alayshaft bearing 73, an idler second gear 61, a double-sided couplingdevice 84, an idler fourth gear 63, a park-lock gearwheel 39, an idlerthird gear 62, a double-sided coupling device 83, an idler first gear60, and a layshaft bearing 73. The lower pinion 51 is fixed onto thelower layshaft 50 at its longitudinal axis. The idler second gear 61,the idler fourth gear 63, the idler third gear 62, and the idler firstgear 60 are mounted on the lower layshaft 50 by bearings separately suchthat these gearwheels become idlers, being free to rotate around thelower layshaft 50. In contrast, the park-lock gearwheel 39 is fixed ontothe lower layshaft 50 coaxially.

The double-sided coupling devices 84 can move along the lower layshaft50 such that it can engage either the idler second gear 61 or the idlerfourth gear 63 to the lower layshaft 50. The double-sided couplingdevice 83 can also move along the lower layshaft 50 such that it canengage either the idler first gear 60 or the idler third gear 62 to thelower layshaft 50. The idler second gear 61 meshes with the fixed wheelsecond gear 30. The idler fourth gear 63 meshes with the fixed wheelfourth gear 31. The idler third gear 62 meshes with the fixed wheelthird gear 25. The idler first gear 60 meshes with the fixed wheel firstgear 24.

There are two double-meshing features provided in the DCT 1. A firstdouble-meshing feature comprises that the fixed wheel fourth gear 31meshes with both the idler fourth gear 63 and the idler sixth gear 65. Asecond double-meshing feature comprises that the fixed wheel second gear30 meshes with both the first reverse gear wheel 35 and the idler secondgear 61.

The park-lock gearwheel 39 comprises a park-lock on the lower layshaft50 that has a final drive pinion 51. The park-lock is the park-lockgearwheel 39 which is provided with a ratchet device, with a clickdevice having a rack element, a pawl or similar. The park-lock keeps thelower layshaft 50, the lower pinion 51, the output gearwheel 12, and theoutput shaft 14 from rotating, which stops a vehicle with the DCT 1 fromrunning when parked. Detailed structure of the park-lock is not shown inFIG. 2.

The DCT 1 with the park-lock is controlled by a gearshift lever locatedin a driving compartment and movable by a vehicle operator betweenpositions corresponding to transmission gear ranges such as Park,Reverse, Neutral, Drive, and Low. A linear actuation cable is attachedat its first end to the gearshift lever, and movement of the gearshiftlever alternatively pushes or pulls on the cable to move a transmissionmode select lever attached to the other end of the cable. The modeselect lever is mechanically connected to a shift valve within a DCThousing, and movement of the shift valve effects shifting betweendifferent gears.

When the gearshift lever is placed in the Park position, two relatedmechanical actuations take place within the DCT 1. First, the modeselect lever is moved to disengage the input shafts 20, 22 from anengine. Second, the park-lock pawl is moved into locking engagement withthe park-lock gearwheel 39 on the lower layshaft 50 to thereby lock theoutput shaft 14 against rotation. A linear actuation cable that actuatesthe mode select lever moves the lock pawl.

A distance 56 between the input shafts 20, 22 and the upper layshaft 40is measured from a common longitudinal axis of the input shafts 20, 22to a longitudinal axis of the upper layshaft 40. Similarly, a distance58 between the input shafts 20, 22 and the lower layshafts 50 ismeasured from the common longitudinal axis of the input shafts 20, 22 toa longitudinal axis of the lower layshaft 50.

The output shaft 14 is further provided further below the lower layshaft50. Two output shaft bearings 75 are installed at two opposite ends ofthe output shaft 14 respectively for supporting. The output gearwheel 12is fixed onto the output shaft 14 coaxially in the middle. The outputgearwheel 12 meshes with the lower pinion 51 and the upper pinion 41.

In the present specification, the expressions “mesh” and “comb” withrespect to geared wheels or engaged gearwheels are provided as synonyms.In a generic sense, a hollow shaft that is disposed inside the hollowinput shaft 22 can replace the solid input shaft 20. The term “couplingdevice” is alternatively termed as “shifting mechanism” or“synchronizer” for engaging or disengaging gearwheels on its carryingshaft. The double-clutch transmission (DCT) is alternatively termed as adouble clutch, or a dual clutch transmission (DCT).

The fixed wheel first gear 24 is also known as the first fixed gearwheel24. Similarly, the fixed wheel third gear 25 is also known as the thirdfixed gearwheel 25. The fixed wheel fifth gear 26 is also known as thefifth fixed gearwheel 26. The fixed wheel seventh gear 27 is also knownas the seventh fixed gearwheel 27. The fixed wheel second gear 30 isalso known the second fixed gearwheel 30. The fixed wheel fourth gear 31is also known as the fourth fixed gearwheel 31. The fixed wheel sixthgear 32 is also known as the sixth fixed gearwheel 32.

Further, the second reverse gear idler wheel 35 is also known as thesecond reverse idler gearwheel 35. The reverse gear idler wheel 37 isalso known as the reverse idler gearwheel 37. The idler first gear 60 isalso known as the first gear idler gearwheel 60. The idler second gear61 is also known as the second gear idler gearwheel 61. The idler thirdgear 62 is also known as the third fixed gearwheel 62. The idler fourthgear 63 is also known as the fourth gear idler gearwheel 63. The idlerfifth gear 64 is also known as the fifth gear idler gearwheel 64. Theidler sixth gear 65 is also known as the sixth gear idler gearwheel 65.The idler seventh gear 66 is also known as the seventh gear idlergearwheel 66.

The output gear wheel 12, the park-lock gearwheel 39, the upper pinion41, the lower pinion 51, and the reverse pinion 55 are known as fixedgearwheels or gear wheels. In addition, the fixed wheel first gear 24,the fixed wheel third gear 25, the fixed wheel fifth gear 26, the fixedwheel seventh gear 27, the fixed wheel second gear 30, the fixed wheelfourth gear 31, the fixed wheel sixth gear 32 are also known as fixedgearwheels or gear wheels.

The upper pinion 41, the lower pinion 51, and the reverse pinion 55 arealternatively known called final drive pinions or final drives. Thepark-lock on the park-lock gearwheel 39 can alternatively be provided onany of the layshafts 38, 40, 50 that has a final drive pinion. Any ofthe input shafts 20, 22 or layshafts 38, 40, 50 can be supported by morethan two bearings.

In the drawings of the present application, dash lines indicate eitheralternative positions of illustrated parts or combing relationshipbetween gearwheels.

The application provides the DCT 1 that permits gearshift operationswith less loss of driving torque. This is because the gearshiftoperations can be achieved by selectively connecting one of the twoclutch discs 8, 10 of the DCT 1. Therefore, an associated additionalmain drive clutch can be avoided. Selective connections between the twoclutch discs 8, 10 also enable the realization of an automatictransmission that can be operated without interruptions in propulsivepower. The propulsive power comprises momentum derived from the rotatinggearwheels and shafts of the DCT 1. Such a transmission is similar indesign to a mechanical manual transmission and it has correspondinglyvery low friction losses. The DCT 1 further provides a parallel manualtransmission that can be used for transverse installation in afront-wheel drive vehicle.

The DCT 1 according to the application can be connected similar to aknown manual transmission, such as a parallel manual transmission. Inthe known manual transmission, a drive shaft for the front axle of avehicle extends outward from its DCT case, and parallel to the outputshaft 14 of the main DCT 1. The arrangement of the known manualtransmission provides little space left for actuation of the manualtransmission and clutch, and for an optional electric motor. Theoptional electric motor can act as a starter device for a combustionengine, as an energy recuperation device for brake operation or as anadditional drive means in hybrid vehicles. Having such little spacepresents difficulties that are solved or that at least alleviated by theapplication. The application provides a DCT 1 that has two clutches forconnecting to an electrical motor and the manual transmissionrespectively in a compact manner.

The application provides a compact structure of a parallel transmission.The parallel transmission includes two input shafts 20, 22, each ofwhich can be non-rotatably coupled to a shaft via its own clutch that ispowered by a drive engine of a vehicle. The DCT 1 of the applicationfurther provides the output shaft 14 that is parallel to the inputshafts 20, 22.

The DCT 1 according to the application is particularly well suited fortransverse installation in front-wheel drive vehicles, in which thefront differential, for example, is positioned below the pinions 41, 51.A short overall length of the power train for transmitting torques canbe achieved.

The application provides at least two relatively small pinions 41, 51 onintermediately arranged layshafts 40, 50 that comb with one relativelybig output gearwheel 12. The output gearwheel 12 in turn is fixed ontothe output shaft 14. This arrangement provides a compact and lightweightDCT 1.

The application further enables a design in which the output gearwheel12 is integrated into a transmission differential device withoutproviding an intermediate output shaft of the DCT 1. This allows a verydense packaging situation for the DCT 1.

It is further not only of advantage to provide the even gearwheels fixedonto one input shaft, but also fix the odd gears onto another inputshaft. This arrangement provides the above-mentioned power-shiftoperation in a smooth and efficient manner when gearshift is performedsequentially. This is because the DCT 1 can alternatively engage one ofthe two clutch discs 8, 10 in the process of increasing or decreasinggear. For example, the power-shift operation from the third gear to thefourth gear causes the solid input shaft 20 and the hollow input shaft22 being engaged alternatively, which is energy efficient and fast.

Some idler gearwheels of the low gears, such as first, second, third, orfourth gear, provided advantageously on the same layshaft 50. In FIG. 2,the idler first gear 60, the idler second gear 61, the idler third gear62 and the idler fourth gear 63 are installed on the same lower layshaft40. In contrast, idler gearwheels of high gears, such as fifth, sixth,or seventh gears, provided on another layshaft. According to FIG. 2, theidler fifth gear 64, the idler sixth gear 65, and the idler seventh gear66 are provided on the same upper layshaft 50. The upper layshaft 40 hashigher rotational speed with smaller diameter for lower torquetransmission, as compared to that of the lower layshaft 50. Thisarrangement eliminates the need of providing multiple layshafts withlarge size for carrying those heavily duty idler gearwheels 60, 61, 62,63 of low gears, such as first, second, third, or fourth gear, on manyshafts respectively. These arrangements offer the feasibility of makingthe DCT 1 lightweight and compact at less cost.

The layshaft bearings 73 of the DCT 1 are next to the pinions 41, 51.The layshaft bearings 73 offer strong support to the pinions 41, 51carrying layshafts 40, 50 for reducing unwanted shaft deflection.Excessive shaft deflection can lower gear transmission efficiency orcause gearwheels' early worn out. The idler shaft bearings 74 next tothe first reverse gear wheel 35 and the second reverse gear wheel 36also provide strong support to the reverse gear idler shaft 38. In alike manner, the output shaft bearings 75 at two opposite ends of theoutput shaft 14 offer sturdy support to the output shaft 14.

In fact, it is also beneficial to provide the idler first gear 60, theidler second gear 61, and the reverse gear idler wheel 37 close to thebearings 73, 74 for supporting. As shown in FIG. 2, the threelayshaft-bearings 73 are immediately adjacent to the idler first gear60, the idler second gear 61, and the reverse gear idler wheel 37respectively for giving strong support to the upper layshaft 40 and thelower layshaft 50. The pinions 41, 51 and especially these gearwheels oflow gears, for example first and second gears, undergo heavier load thanthose of the higher gears, for example fifth, sixth, and seventh gears,because drive ratios are higher for the lower gears and reverse gears.Therefore, a carrying shaft of low gears, such as the lower layshaft 50,must take up stronger driving torques and carry heavier gearwheels withlarger sizes. If those loads are taken up close to the supportingbearings of the shafts, their load-carrying shafts' bending will bereduced.

FIG. 2 illustrates the path of torque flow of a first gear transmissionratio. In FIG. 2, an input torque of the first gear is received from acrankshaft 2 of a combustion engine that is not shown. According to FIG.2, the solid input shaft 20 from the double-clutch 6 of the DCT 1receives the input torque of the first gear. The torque of the firstgear is transmitted from the solid input shaft 20, via the fixed wheelfirst gear 24, via the idler first gear 60, via the double-sidedcoupling device 83, via the lower layshaft 50, via lower pinion 51, andvia the output gear wheel 12 to the output shaft 14. The double-sidedcoupling device 83 engages the idler first gear 60 to the lower layshaft50 when transmitting the torque of the first gear, which provides thefirst gear of the DCT 1. The number of tooth engagements or engaged gearpairs for the torque transfer of the first gear is two.

FIG. 3 illustrates the path of torque flow of a second gear transmissionratio. In FIG. 3, an input torque of the second gear is received fromthe crankshaft 2 of the combustion engine that is not shown. Accordingto FIG. 3, the hollow input shaft 20 from the double-clutch 6 of the DCT1 receives the input torque of the second gear. The torque of the secondgear is transmitted from the hollow input shaft 22, via the fixed wheelsecond gear 30, via the idler second gear 61, via the double-sidedcoupling device 84, via the lower layshaft 50, via the lower pinion 51,and via the output gearwheel 12 to the output shaft 14. The double-sidedcoupling device 84 engages the idler second gear 61 to the lowerlayshaft 50 when transmitting the torque of the second gear, whichprovides the second gear of the DCT 1. The number of tooth engagementsor engaged gear pairs for the torque transfer of the second gear is two.

FIG. 4 illustrates the path of torque flow of a third gear transmissionratio. In FIG. 4, an input torque of the third gear is received from thecrankshaft 2 of the combustion engine that is not shown. According toFIG. 4, the solid input shaft 20 from the double clutch of the DCT 1receives the input torque of the third gear. The torque of the thirdgear is transmitted from the solid input shaft 20, via the fixed wheelthird gear 25, via the idler third gear 62, via the double-sidedcoupling device 83, via the lower layshaft 50, via the lower pinion 51,and via the output gear wheel 12 to the output shaft 14. Thedouble-sided coupling device 83 engages the idler wheel third gear 62 tothe lower layshaft 50 when transmitting the torque of the third gear,which provides the third gear of the DCT 1. The number of toothengagements or engaged gear pairs for the torque transfer of the thirdgear is two.

FIG. 5 illustrates the path of torque flow of a fourth gear transmissionratio. In FIG. 5, an input torque of the fourth gear is received fromthe crankshaft 2 of the combustion engine that is not shown. Accordingto FIG. 5, the hollow input shaft 22 from the double-clutch 6 of the DCT1 receives the input torque of the fourth gear. The torque of the fourthgear is transmitted from the hollow input shaft 22, via the fixed wheelfourth gear 31, via the idler fourth gear 63, via the double-sidedcoupling device 84, via the lower layshaft 50, via the lower pinion 51,and via the output gearwheel 12 to the output shaft 14. The double-sidedcoupling device 84 engages the idler fourth gear 63 to the lowerlayshaft 50 when transmitting the torque of the fourth gear, whichprovides the fourth gear of the DCT 1. The number of tooth engagementsor engaged gear pairs for the torque transfer of the fourth gear is two.

FIG. 6 illustrates the path of torque flow of a fifth gear transmissionratio. In FIG. 6, an input torque of the fifth gear is received from thecrankshaft 2 of a combustion engine that is not shown. According to FIG.6, the solid input shaft 20 from the double-clutch 6 of the DCT 1receives the input torque of the fifth gear. The torque of the fifthgear is transmitted from the solid input shaft 20, via the fixed wheelfifth gear 26, via the idler fifth gear 64, via the double-sidedcoupling device 82, via the upper layshaft 40, via the upper pinion 41,and via the output gearwheel 12 to the output shaft 14. The double-sidedcoupling device 82 engages the idler fifth gear 64 to the upper layshaft40 when transmitting the torque of the fifth gear, which provides thefifth gear of the DCT 1. The number of tooth engagements or engaged gearpairs for the torque transfer of the fifth gear is two.

FIG. 7 illustrates the path of torque flow of a sixth gear transmissionratio. In FIG. 7, an input torque of the sixth gear is received from thecrankshaft 2 of a combustion engine that is not shown. According to FIG.7, the hollow input shaft 22 from the double-clutch 6 of the DCT 1receives the input torque of the sixth gear. The torque of the sixthgear is transmitted from the hollow input shaft 22, via the fixed wheelsixth gear 32, via the idler sixth gear 65, via the double-sidedcoupling device 81, via the upper layshaft 40, via the upper pinion 41,and via the output gear wheel 12 to the output shaft 14. Thedouble-sided coupling device 81 engages the idler sixth gear 65 to theupper layshaft 40 when transmitting the torque of the sixth gear, whichprovides the sixth gear of the DCT 1. The number of tooth engagements orengaged gear pairs for the torque transfer of the sixth gear is two.

FIG. 8 illustrates the path of torque flow of a seventh geartransmission ratio. In FIG. 8, an input torque of the seventh gear isreceived from the crankshaft 2 of a combustion engine that is not shown.According to FIG. 8, the solid input shaft 20 from the double-clutch 6of the DCT 1 receives the input torque of the seventh gear. The torqueof the seventh gear is transmitted from the solid input shaft 20, viathe fixed wheel seventh gear 27, via the idler seventh gear 66, via thedouble-sided coupling device 82, via the upper layshaft 40, via theupper pinion 41, and via the output gearwheel 12 to the output shaft 14.The double-sided coupling device 82 engages the idler seventh gear 66 tothe upper layshaft 40 when transmitting the torque of the seventh gear,which provides the seventh gear of the DCT 1. The number of toothengagements or engaged gear pairs for the torque transfer of the seventhgear is two.

FIG. 9 illustrates the path of torque flow of a reverse geartransmission ratio. In FIG. 9, an input torque of the reverse gear isreceived from the crankshaft 2 of a combustion engine that is not shown.According to FIG. 9, the hollow input shaft 22 from the double-clutch 6of the DCT 1 receives the input torque of the reverse gear. The torqueof the reverse gear is transmitted from the hollow input shaft 22, viathe fixed wheel second gear 30, via the first reverse gear wheel 35, viathe reverse gear idler shaft 38, via the second reverse gear wheel 36,and via the reverse gear idler wheel 37. Then, the torque is transmittedvia the double-sided coupling device 81, via the upper layshaft 40, viathe upper pinion 41, and via the output gearwheel 12 to the output shaft14. The double-sided coupling device 81 engages the reverse gear idlerwheel 37 to the upper layshaft 40 when transmitting the torque of thereverse gear ratio, which provides the reverse gear of the DCT 1. Thenumber of tooth engagements or engaged gear pairs for the torquetransfer of the reverse gear is three.

FIG. 10 illustrates an assembly 100 of a double-sided coupling device102 with its neighboring gearwheels 101, 103 for engagement. Theassembly 100 comprises a shaft 104 with the two coaxially mounted idlergears 101, 103 on two bearings respectively. The coupling device 102 isprovided between the idler gear 101 on the left and the idler gear 103on the right. The coupling device 102 is configured to move along theshaft 104 to selectively engage any of the idler gears 101, 103 at onetime. In other words, the idler gears 101, 103 can alternatively bebrought into non-rotating engagement with the shaft 104 by the couplingdevice 102. Symbols for showing the assembly 100 is provided at theright hand side of FIG. 10.

FIG. 11 illustrates an assembly 110 of a single-sided coupling device112 with its neighboring gearwheel 113 for engagement. The assembly 110comprises a shaft 114 with the one coaxially mounted idler gear 113 on abearing. The coupling device 112 is provided next to the idler gear 113on the left side. The coupling device 112 is configured to move alongthe shaft 114 to engage or disengage the idler gears 113. In otherwords, the idler gear 113 can be brought into non-rotating engagementwith the shaft 114 by the single-sided coupling device 112. Symbols forshowing the assembly 110 are provided at the right hand side of FIG. 11.

FIG. 12 illustrates an assembly 120 of an idler gearwheel 121 that isrotatably supported by a shaft 122 on a bearing 123. The idler gearwheel121 is coaxially mounted onto the shaft 122 via the bearing 123. Thebearing 123 enables the idler gearwheel 121 to be freely rotated aroundthe shaft 122. Symbols that represent the assembly 120 are provided atthe right hand side of the FIG. 12.

FIG. 13 illustrates an assembly 130 of a fixed gearwheel 132 that issupported on a shaft 131. The fixed gearwheel 132 is coaxially mountedonto the shaft 131 such that the gearwheel 132 is fixed to the shaft131. The fixed gearwheel 132 and the shaft 131 are joined as one singlebody such that torque of the fixed gearwheel 132 is transmitted to theshaft 131 directly, and vice versa.

A number of fixed gearwheels are rigidly connected to the input shafts20, 22 and other shafts 14, 38, 40, 50 in a manner that is similar tothe assembly 130. A symbol as used in the previous figures for such afixed gearwheel is provided on the left side in FIG. 13. The morecommonly used symbol for such a fixed gearwheel is provided on the rightside in FIG. 13.

FIG. 14 illustrates a cross-section through a detail of a crankshaft 2of an internal combustion engine according to the embodiment of the DCT1. According to FIG. 14, the crankshaft 2 of the internal combustionengine, which is not shown here, is non-rotatably connected to a housing4 of a double clutch 6. The double clutch 6 includes an inner clutchdisc 8 and an outer clutch disc 10, which can be brought intonon-rotating engagement with the housing 4 via control elements that arenot illustrated here. The solid input shaft 20 can be non-rotatablyconnected to the inner clutch disc 8, and extends all the way throughthe hollow shaft 22. Similarly, the hollow input shaft 22 can benon-rotatably connected to the outer clutch disc 10. The inner clutchdisc 8 is also known as the inner clutch, whilst the outer clutch disc10 is also known as the outer clutch. The input shafts 20, 22 compriseends 5 that are connected to the two clutch discs 8, 10. These ends arealso termed as clutch disc ends 5 of the input shafts.

An outer diameter around the inner clutch disc 8 is larger than an outerdiameter around the outer clutch disc 10. Correspondingly, an outerdiameter of the inner clutch disc 8 is larger than an outer diameter ofthe outer clutch disc 10.

The above-mentioned nine torque flow paths not only provide viablesolutions to generate nine gears of the DCT 1, but also offerpossibilities of switching from one gear to the another efficiently. Thegear switching can be achieved by switching between the two inputshafts, between gearwheels of a double meshing feature, or incombination of both.

For example, the DCT 1 can provide odd gears (i.e. 1st, 3rd, 5th & 7thgears) by driving the gearwheels of the DCT 1 using the solid inputshaft 20. The DCT 1 also can provide even gears (i.e. 2nd, 4th & 6thgears) by driving the gearwheels of the

DCT 1 using the hollow input shaft 22. Gear switching between the oddand the even can simply be obtained by alternating between the two inputshafts 20, 22.

One double meshing feature provides efficient and fast gear switchingbetween gears of two driven gearwheels that comb with a shared drivinggearwheel. For example, the DCT 1 provides the convenience of selectingthe fourth gear or the sixth gear without stopping their shared drivinggearwheel, namely the fixed wheel fourth gear 31. The selection can beachieved by engaging either the driven idler fourth gear 63 or thedriven idler sixth gear 65.

The double-meshing feature of the fixed wheel fourth gear 31 reduces thenumber of driving gearwheels, which is commonly engaged by the drivengearwheels idler fourth gear 63 and the driven gearwheel idler sixthgear 65. For example, the fixed wheel fourth gear 31 and the fixed wheelsixth gear 32 as driving gear wheels become one single gearwheel that isshared by the idler fourth gear 63 and the idler sixth gear 65. As aresult, the number of gearwheels on the hollow input shaft 22 has beenreduced by one gearwheel and less space is required on the hollow inputshaft 22 so that the DCT 1 can be made cheaper and lighter.

The park-lock gearwheel 39 comprises a park-lock on the lower layshaft50 that carries a final drive pinion 51. The park-lock is a wheel whichis provided with a ratchet device, with a click device having a rackelement, a claw or similar. The park-lock keeps the lower layshaft 50,the lower pinion 51, the output gear wheel 12, and the output shaft 14from rotating, which stops a vehicle with the DCT 1 from running whenparked. Detailed structure of the park-lock is not shown.

In providing gear meshing or combing for torque transmission, lessnumber of gear tooth engagement, that is gear engagement, is preferred.The less number of gear tooth engagement provides lower noise and moreefficient torque transmission. Examples of the less gear toothengagement are provided in FIGS. 2-9.

The DCT 1 drives the gearwheel groups of the first gear and the reversegear by different input shafts 20, 22. A vehicle with the DCT 1 can movebetween a slow forward mode and a slow backward mode by engaging anddisengaging the respective clutch discs 8, 10, which are connected tothe two input shafts 20, 22 respectively. The DCT 1 enables the vehicleto move back and forth quickly with little loss of the transmissionpower or gearwheels momentum. This scheme helps in many situations inwhich a wheel of the vehicle is stuck in a hostile environment such as asnow hole or a mud hole. The vehicle can then be swayed free just byswitching between the two clutch discs 8, 10.

FIGS. 15-16 illustrate a further embodiment of the application. Theembodiment includes parts that are similar to the parts of previouslydescribed embodiment. The similar parts are labeled with the same orsimilar part reference number. Descriptions related to the similar partsare hereby incorporated by reference.

FIG. 15 shows a front view of the gearbox of the application. Arelatively big output gearwheel 12 on an output shaft 14 meshes with alower pinion 51, which is provided on a lower layshaft 50. The outputgearwheel 12 further meshes with an upper pinion 41, which is providedon an upper layshaft 40. A reverse gear idler shaft 38, a solid inputshaft 20, and a hollow output shaft 22 are provided in parallel with thelayshafts 40, 50. In some variants of the application, at least one afurther layshaft with a further pinion can be provided but this is notshown here. Such a further pinion would then also mesh or comb with theoutput gearwheel 12.

FIG. 15 further comprises a cutting plane A-A for illustrating thecross-section through the gearbox, which is shown in FIG. 16. For anembodiment, which has more than two layshafts or an additional idlershaft, a cutting plane, which leads through all shafts, is appliedsimilarly. One of the goals of FIG. 16 is to illustrate further thestructure and the torque flows through the embodiment of the gearbox.

FIG. 16 illustrates a simplified cross-section through the double clutchtransmission gearbox 1 of FIG. 15. It illustrates structure and varioustorque flows for the several gears of the double clutch transmissiongearbox 1.

The double clutch transmission gearbox 1 comprises the following shafts,from top to bottom, the output shaft 14, the upper layshaft 40, thehollow shaft 22, the solid input shaft 20, the lower layshaft 50, andthe reverse gear idler shaft 38.

The above-mentioned shafts are provided parallel to each other atpredetermined mutual distances inside the gearbox 1. The hollow shaft 22is arranged concentrically around the solid shaft 20. The solid inputshaft 20 protrudes outside the hollow input shaft 22 at both ends.

The solid input shaft 20 comprises, from the right end to the left end,a solid shaft bearing 71, a hollow shaft bearing 72, a fixed wheel thirdgear 25, a fixed wheel fifth gear 26, a fixed wheel first gear 24, afixed wheel seventh gear 27, and a solid shaft bearing 71. The hollowshaft bearing 72 serves also as solid shaft bearing 71.

The hollow input shaft 22 comprises, from the right end to the left end,a hollow shaft bearing 72, a fixed wheel second gear 30, a fixed wheelfourth gear 31, which also serves as a fixed wheel sixth gear 32, andthe hollow shaft bearing 72, which also serves as the solid shaftbearing 71.

The upper layshaft 40 comprises, from the right end to the left end, theupper pinion 41, a layshaft bearing 73, an idler second gear 61, adouble-sided coupling device 80, an idler fifth gear 64, an idler thirdgear 62, a double-sided coupling device 81, an idler first gear 60, anda layshaft bearing 73. The idler second gear 61 meshes with the fixedwheel second gear 30. The idler fifth gear 64 meshes with the fixedwheel fourth gear 31. The idler third gear 62 meshes with the fixedwheel third gear 25. The idler first gear 60 meshes with the fixed wheelfirst gear 24. The double-sided coupling device 80 is configured to movethe along the upper layshaft 40 for engaging either attached the idlersecond gear 61 or the idler fifth gear 64 to the upper layshaft 40. Thedouble-sided coupling device 81 is also configured to move along theupper layshaft 40 for engaging either the idler third gear 62 or theidler first gear 60 to the upper layshaft 40.

The lower layshaft 50 comprises, from the right end to the left end, thelower pinion 51, a layshaft bearing 73, an reverse gear idler wheel 37,a double-sided coupling device 83, an idler sixth gear 65, a park-lockgearwheel 39, an idler fifth gear 64, a double-sided coupling device 82,an idler seventh gear 66, and a layshaft bearing 73. The idler sixthgear 65 meshes with the fixed wheel sixth gear 32. The idler fifth gear64 meshes with the fixed wheel fifth gear 26. The idler seventh gear 66meshes with the fixed wheel seventh gear 27. The double-sided couplingdevice 83 is configured to move along the lower layshaft 50 for engagingeither the reverse gear idler wheel 37 or the idler sixth gear 65 to thelower layshaft 50. The double-sided coupling device 82 is alsoconfigured to move along the lower layshaft 50 for engaging either theidler fifth gear 64 or the idler seventh gear 66 to the lower layshaft50.

The reverse gear idler shaft 38 comprises, from the right end to theleft end, an idler shaft bearing 74, a first reverse gear wheel 35, asecond reverse gear wheel 36, and an idler shaft bearing 74. The firstreverse gear wheel 35 meshes with the fixed wheel second gear 30. Thesecond reverse gear wheel 36 meshes with the reverse gear idler wheel37.

FIG. 16 also shows a clutch housing 4 that encloses gearwheels of thedouble-clutch transmission 1. The clutch housing 4 comprises severalwalls 3, 6 that are closely neighboring to the gearwheels of thedouble-clutch transmission 1. In particular, a sidewall 6 of the clutchhousing 4 is located near the first gear idler gearwheel 60 at an end ofthe upper layshaft 40. The first gear idler gearwheel 60 resides on theend that is opposite to an end of on the upper layshaft 40 fixed withthe upper pinion 41.

In FIG. 16, the idler seventh gear 66 is mounted on the left end of thelower layshaft 50, which is opposite to the end that carries lowerpinion 51. The idler seventh gear 66 has the smallest diameter ascompared to that of the idler of other gears 60, 61, 62, 63, 64, 65.Putting the idler seventh gear 66 at the end enables the sidewall 3 tobe closer to the lower layshaft 50, as compared to the situation ofputting the idler of other gears 60, 61, 62, 63, 64, 65 at this end.

Therefore, in order to make the double-clutch transmission 1 to be morecompact, it is beneficial to mount idlers of different gears on alayshaft from a low gear to a high gear sequentially, starting from anend of the layshaft with a pinion to a remote end of the layshaft.Furthermore, it is further advantageous to mount fixed gearwheels ofdifferent gears an input shaft 20, 22 from a high gear to a low gearsequentially, starting from an end of the input shaft 20, 22 forconnecting to a crankshaft 2. A fixed gearwheel of a high gear on theinput shaft 20, 22 is larger than that of a low gear.

Torque flow of the first gear according to FIG. 16 starts from the solidinput shaft 22, via the fixed wheel first gear 24, via the idler firstgear 60, via the double-sided coupling device 81, via the upper layshaft40, via the upper pinion 41, via the output gear wheel 12, to the outputshaft 14.

Torque flow of the second gear according to FIG. 16 starts from thehollow input shaft 22, via the fixed wheel second gear 30, via the idlersecond gear 61, via the double-sided coupling device 80, via the upperlayshaft 40, via the upper pinion 41, via the output gear wheel 12, tothe output shaft 14.

Torque flow of the third gear according to FIG. 16 starts from the solidinput shaft 20, via the fixed wheel third gear 25, via the idler thirdgear 62, via the double-sided coupling device 81, via the upper layshaft40, via the upper pinion 41, via the output gear wheel 12, to the outputshaft 14.

Torque flow of the fourth gear according to FIG. 16 starts from thehollow input shaft 22, via the fixed wheel fourth gear 31, via the idlerfourth gear 63, via the double-sided coupling device 80, via the upperlayshaft 40, via the upper pinion 41, via the output gear wheel 12, tothe output shaft 14.

Torque flow of the fifth gear according to FIG. 16 starts from the solidinput shaft 20, via the fixed wheel fifth gear 26, via the idler fifthgear 64, via the double-sided coupling device 82, via the lower layshaft50, via the lower pinion 51, via the output gear wheel 12, to the outputshaft 14.

Torque flow of the sixth gear according to FIG. 16 starts from thehollow input shaft 22, via the fixed wheel sixth gear 32, via the idlersixth gear 65, via the double-sided coupling device 83, via the lowerlayshaft 50, via the lower pinion 51, via the output gear wheel 12, tothe output shaft 14.

Torque flow of the seventh gear according to FIG. 16 starts from thesolid input shaft 20, via the fixed wheel seventh gear 27, via the idlerseventh gear 66, via the double-sided coupling device 82, via the lowerlayshaft 50, via the lower pinion 51, via the output gear wheel 12, tothe output shaft 14.

Torque flow of the reverse gear according to FIG. 16 starts from thehollow input shaft 22, via the fixed wheel second gear 30, via the firstreverse gear wheel 35, via the reverse gear idler shaft 38, via thesecond reverse gear wheel 36, and via the reverse gear idler wheel 37.The torque is then transmitted via the double-sided coupling device 83,via the lower layshaft 50, via the lower pinion 51, and via the outputgear wheel 12 to the output shaft 14.

FIGS. 17-18 illustrate a further embodiment of the application. Theembodiment includes parts that are similar to the parts of previouslydescribed embodiment. The similar parts are labeled with the same orsimilar part reference number. Descriptions related to the similar partsare hereby incorporated by reference.

FIGS. 17-18 illustrate a further embodiment of the application. Theembodiment includes parts that are similar to the parts of previouslydescribed embodiment. The similar parts are labeled with the same orsimilar part reference number. Descriptions related to the similar partsare hereby incorporated by reference.

FIG. 17 shows a front view of the gearbox of the application. Arelatively big output gearwheel 12 on an output shaft 14 meshes with alower pinion 51, which is provided on a lower layshaft 50. The outputgearwheel 12 further meshes with an upper pinion 41, which is providedon an upper layshaft 40. A reverse gear idler shaft 38, a solid inputshaft 20, and a hollow output shaft 22 are provided in parallel with thelayshafts 40, 50. In some variants of the application, at least one afurther layshaft with a further pinion can be provided but this is notshown here. Such a further pinion would then also mesh or comb with theoutput gearwheel 12.

FIG. 17 further comprises a cutting plane A-A for illustrating thecross-section through the gearbox, which is shown in FIG. 18. For anembodiment, which has more than two layshafts or an additional idlershaft, a cutting plane, which leads through all shafts, is appliedsimilarly. One of the goals of FIG. 18 is to illustrate further thestructure and the torque flows through the embodiment of the gearbox.

FIG. 18 illustrates a simplified cross-section through the double clutchtransmission gearbox 1 of FIG. 17. It illustrates structure and varioustorque flows for the several gears of the double clutch transmissiongearbox 1.

The double clutch transmission gearbox 1 comprises the following shafts,from top to bottom, the output shaft 14, the upper layshaft 40, thehollow shaft 22, the solid input shaft 20, the lower layshaft 50 and thereverse gear idler shaft 38.

The above-mentioned shafts are provided parallel to each other atpredetermined mutual distances inside the gearbox 1. The hollow shaft 22is arranged concentrically around the solid shaft 20. The solid inputshaft 20 protrudes outside the hollow input shaft 22 at both ends.

The solid input shaft 20 comprises, from the right end to the left end,a solid shaft bearing 71, a hollow shaft bearing 72, which serves alsoas solid shaft bearing 71, a fixed wheel third gear 25, a fixed wheelfifth gear 26, a fixed wheel seventh gear 27, a fixed wheel first gear24, and a solid shaft bearing 71.

The hollow input shaft 22 comprises, from the right end to the left end,a hollow shaft bearing 72, a fixed wheel second gear 30, a fixed wheelfourth gear 31, which also serves as a fixed wheel sixth gear 32, andthe hollow shaft bearing 72, which also serves as the solid shaftbearing 71.

The upper layshaft 40 comprises, from the right end to the left end, theupper pinion 41, a layshaft bearing 73, an idler second gear 61, adouble-sided coupling device 80, an idler fifth gear 64, an idler thirdgear 62, a double-sided coupling device 81, an idler first gear 60, anda layshaft bearing 73. The idler second gear 61 meshes with the fixedwheel second gear 30. The idler fifth gear 64 meshes with the fixedwheel fourth gear 31. The idler third gear 62 meshes with the fixedwheel third gear 25. The idler first gear 60 meshes with the fixed wheelfirst gear 24. The double-sided coupling device 80 is configured to movethe along the upper layshaft 40 for engaging either attached the idlersecond gear 61 or the idler fifth gear 64 to the upper layshaft 40. Thedouble-sided coupling device 81 is also configured to move along theupper layshaft 40 for engaging either the idler third gear 62 or theidler first gear 60 to the upper layshaft 40.

The lower layshaft 50 comprises, from the right end to the left end, thelower pinion 51, a layshaft bearing 73, an reverse gear idler wheel 37,a double-sided coupling device 83, an idler sixth gear 65, a park-lockgearwheel 39, an idler fifth gear 64, a double-sided coupling device 82,an idler seventh gear 66, and a layshaft bearing 73. The idler sixthgear 65 meshes with the fixed wheel sixth gear 32. The idler fifth gear64 meshes with the fixed wheel fifth gear 26. The idler seventh gear 66meshes with the fixed wheel seventh gear 27. The double-sided couplingdevice 83 is configured to move along the lower layshaft 50 for engagingeither the reverse gear idler wheel 37 or the idler sixth gear 65 to thelower layshaft 50. The double-sided coupling device 82 is alsoconfigured to move along the lower layshaft 50 for engaging either theidler fifth gear 64 or the idler seventh gear 66 to the lower layshaft50.

The reverse gear idler shaft 38 comprises, from the right end to theleft end, an idler shaft bearing 74, a first reverse gear wheel 35, asecond reverse gear wheel 36, and an idler shaft bearing 74. The firstreverse gear wheel 35 meshes with the fixed wheel second gear 30. Thesecond reverse gear wheel 36 meshes with the reverse gear idler wheel37.

FIG. 18 also shows a clutch housing 4 that encloses gearwheels of thedouble-clutch transmission 1. The clutch housing 4 comprises severalwalls 3, 7 that are closely neighboring to the gearwheels of thedouble-clutch transmission 1. In particular, a sidewall 7 of the clutchhousing 4 is located near the first gear idler gearwheel 60 at an end ofthe upper layshaft 40. The first gear idler gearwheel 60 resides on theend that is opposite to an end of on the upper layshaft 40 fixed withthe upper pinion 41.

Compared to the clutch housing 4 of FIG. 16, the sidewall 6 of FIG. 16is closer to the upper layshaft 40 than the sidewall 7 of FIG. 18. Thisis because the fixed wheel first gear 24 is at a left side of the fixedwheel seventh gear 27. The largest idler of seven gears 60 forces thesidewall 7 to be further away from the upper layshaft 40. In short, theclutch housing 4 of FIG. 16 is more compact than that of the FIG. 18.

Torque flow paths of seven forward gears and one reverse gear of thepresent embodiment in FIGS. 17-18 are similar to that of the FIGS.15-16.

Although the above description contains much specificity, these shouldnot be construed as limiting the scope of the embodiments but merelyproviding illustration of the foreseeable embodiments. Especially theabove stated advantages of the embodiments should not be construed aslimiting the scope of the embodiments but merely to explain possibleachievements if the described embodiments are put into practice. Thus,the scope of the embodiments should be determined by the claims, ratherthan by the examples given.

While at least one exemplary embodiment has been presented in theforegoing summary and detailed description, it should be appreciatedthat a vast number of variations exist. It should also be appreciatedthat the exemplary embodiment or exemplary embodiments are onlyexamples, and are not intended to limit the scope, applicability, orconfiguration in any way. Rather, the foregoing summary and detaileddescription will provide those skilled in the art with a convenient roadmap for implementing an exemplary embodiment of the invention, it beingunderstood that various changes may be made in the function andarrangement of elements described in an exemplary embodiment withoutdeparting from the scope as set forth in the appended claims and theirlegal equivalents.

1. A double-clutch transmission, comprising: an inner input shaft and anouter input shaft, at least a portion of the inner input shaft beingsurrounded by the outer input shaft; a first clutch disc connected tothe inner input shaft and a second clutch disc connected to the outerinput shaft; a first layshaft, a second layshaft and a third layshaftspaced apart from the inner input shaft and the outer input shafts andarranged substantially parallel to the inner input shaft and the outerinput shafts; at least one of the first layshaft, the second layshaft,or the third layshaft comprises a pinion; gearwheels arranged on thefirst layshaft, on the second layshaft, the third layshaft, on the innerinput shaft and on the outer input shaft, the gearwheels comprising afirst gearwheel group, a second gearwheel group, a third gearwheelgroup, a fourth gearwheel group, a fifth gearwheel group, a sixthgearwheel group, a seventh gearwheel group adapted to provide sevensequentially increasing forward gears, the first gearwheel groupcomprising a first fixed gearwheel on the inner input shaft, meshingwith a first gear idler gearwheel on one of the first layshaft, thesecond layshaft, or the third layshaft and adapted to provide a firstforward gear, the third gearwheel group comprising a third fixedgearwheel on the inner input shaft, meshing with a third gear idlergearwheel on one of the first layshaft, the second layshaft, or thethird layshaft and adapted to provide a third forward gear, the fifthgearwheel group comprising a fifth fixed gearwheel on the inner inputshaft, meshing with a fifth gear idler gearwheel on one of the firstlayshaft, the second layshaft, or the third layshaft and adapted toprovide a fifth forward gear, the seventh gearwheel group comprising aseventh fixed gearwheel on the inner input shaft, meshing with a seventhgear idler gearwheel on one of the first layshaft, the second layshaft,or the third layshaft adapted to provide a seventh forward gear, thesecond gearwheel group comprising a second fixed gearwheel on the outerinput shafts, meshing with a second gear idler gearwheel on one of thefirst layshaft, the second layshaft, or the third layshaft and adaptedto provide a second forward gear, the fourth gearwheel group comprisinga fourth fixed gearwheel on the outer input shafts, meshing with afourth gear idler gearwheel on one of the first layshaft, the secondlayshaft, or the third layshaft and adapted to provide a fourth forwardgear, the sixth gearwheel group comprising a sixth fixed gearwheel onthe outer input shafts, meshing with a sixth gear idler gearwheel on oneof the first layshaft, the second layshaft, or the third layshaft andadapted to provide a sixth forward gear, and each gearwheel groupcomprising a coupling device arranged on one of the first layshaft, thesecond layshaft, or the third layshaft and adapted to selectively engageone of the gearwheels for selecting one of the seven gears, and thefourth fixed gearwheel further meshing with the sixth gear idlergearwheel; a park-lock gearwheel fixed onto one of the first layshaft,the second layshaft, or the third layshafts that is adapted to carry afinal drive pinion.
 2. The double-clutch transmission according to claim1, wherein one of the fixed gearwheel of a lower gear is closer to theclutch disc ends of the input shafts than another one of the fixedgearwheel of a higher gear.
 3. The double-clutch transmission accordingto claim 1, wherein one of the idler gearwheels of a lower gear iscloser to the pinion than another one of the idler gearwheels of ahigher gear on their shared layshaft.
 4. The double-clutch transmissionaccording to claim 1, wherein the first forward gear and the reversegear are provided by the different input shafts.
 5. The double-clutchtransmission device according to claim 1, wherein the gearwheels furthercomprises a reverse gearwheel group that comprises a reverse fixedgearwheel on one of the input shafts, meshing with a first reverse gearwheel on the third layshaft for receiving an input reverse torque, thereverse gearwheel group further comprises a second reverse gear wheel onthe third layshaft that meshes with one of the idler gearwheels on oneof the first layshaft and the second layshaft for outputting thereceived reverse torque to the pinion, and the reverse gearwheel groupfurther comprises a coupling device on one of the layshafts to engagethe gearwheels of the reverse gear for selecting the reverse gear. 6.The double-clutch transmission device according to claim 1, furthercomprising two pinions that are mounted on two of the layshafts,respectively.
 7. The double-clutch transmission device according to oneof the preceding claims, wherein at least two of the first gear idlergearwheel, the second gear idler gearwheel, the third gear idlergearwheel and the fourth gear idler gearwheel are mounted on one of thesame layshaft.
 8. The double-clutch transmission device according toclaim 1, wherein at least two of the fifth gear idler gearwheel, thesixth gear idler gearwheel and the seventh gear idler gearwheel aremounted on one of the same layshaft.
 9. The double-clutch transmissionaccording to claim 1 further comprising bearings adapted to support thelayshafts, at least one of the bearings being provided next to thepinion.
 10. The double-clutch transmission according to claim 8, whereinat least one of the bearings is provided next to one of the drivengearwheels of low gears and the reverse gear.
 11. A gearbox comprising:double-clutch transmission, the double-clutch transmission comprising:an inner input shaft and an outer input shaft, at least a portion of theinner input shaft surrounded by the outer input shaft; a first clutchdisc connected to the inner input shaft and a second clutch discconnected to the outer input shaft; a first layshaft, a second layshaftand a third layshaft spaced apart from the inner input shaft and theouter input shaft and arranged substantially parallel to the inner inputshaft and the outer input shaft; at least one of the first layshaft, thesecond layshaft, or the third layshaft comprises a pinion; gearwheelsarranged on the first layshaft, on the second layshaft, on the thirdlayshaft, on the inner input shaft, and on the outer input shaft, thegearwheels comprising a first gearwheel group, a second gearwheel group,a third gearwheel group, a fourth gearwheel group, a fifth gearwheelgroup, a sixth gearwheel group, a seventh gearwheel group adapted toprovide seven sequentially increasing forward gears, the first gearwheelgroup comprising a first fixed gearwheel on the inner input shaft,meshing with a first gear idler gearwheel on one of the first layshaft,the second layshaft, or the third layshaft and adapted to provide afirst forward gear, the third gearwheel group comprising a third fixedgearwheel on the inner input shaft, meshing with a third gear idlergearwheel on one of the first layshaft, the second layshaft, or thethird layshaft and adapted to provide a third forward gear, the fifthgearwheel group comprising a fifth fixed gearwheel on the inner inputshaft, meshing with a fifth gear idler gearwheel on one of the firstlayshaft, the second layshaft, or the third layshaft and adapted toprovide a fifth forward gear, the seventh gearwheel group comprising aseventh fixed gearwheel on the inner input shaft, meshing with a seventhgear idler gearwheel on one of the first layshaft, the second layshaft,or the third layshaft and adapted to provide a seventh forward gear, thesecond gearwheel group comprising a second fixed gearwheel on the outerinput shafts, meshing with a second gear idler gearwheel on one of thefirst layshaft, the second layshaft, or the third layshaft and adaptedto provide a second forward gear, the fourth gearwheel group comprisinga fourth fixed gearwheel on the outer input shafts, meshing with afourth gear idler gearwheel on one of the first layshaft, the secondlayshaft, or the third layshaft and adapted to provide a fourth forwardgear, the sixth gearwheel group comprising a sixth fixed gearwheel onthe outer input shafts, meshing with a sixth gear idler gearwheel on oneof the first layshaft, the second layshaft, or the third layshafts andadapted to provide a sixth forward gear, and each gearwheel groupcomprising a coupling device arranged on one of the first layshaft, thesecond layshaft, or the third layshaft and adapted to selectively engageone of the gearwheels for selecting one of the seven gears, and thefourth fixed gearwheel further meshing with the sixth gear idlergearwheel; a park-lock gearwheel fixed onto one of the first layshaft,the second layshaft, or the third layshafts that is adapted to carry afinal drive pinion; and an output gearwheel on an output shaft thatmeshes with the pinions for outputting a drive torque to a torque drain.12. The power train device according to claim 11, the power train devicefurther comprising at least one power source for generating a drivingtorque.
 13. The power train device according to claim 12, wherein thepower source comprises a combustion engine.
 14. The power train deviceof claim 12, wherein the power source comprises an electric motor. 15.(canceled)